The involvement of calcium carriers and of the vacuole in the glucose-induced calcium signaling and activation of the plasma membrane H+-ATPase in Saccharomyces cerevisiae cells.

Abstract

Previous work from our laboratories demonstrated that the sugar-induced activation of plasma membrane H+-ATPase in Saccharomyces cerevisiae is dependent on calcium metabolism with the contribution of calcium influx from external medium. Our results demonstrate that a glucose-induced calcium (GIC) transporter, a new and still unidentified calcium carrier, sensitive to nifedipine and gadolinium and activated by glucose addition, seems to be partially involved in the glucose-induced activation of the plasma membrane H+-ATPase. On the other hand, the importance of calcium carriers that can release calcium from internal stores was analyzed in glucose-induced calcium signaling and activation of plasma membrane H+-ATPase, in experimental conditions presenting very low external calcium concentrations. Therefore the aim was also to investigate how the vacuole, through the participation of both Ca2+-ATPase Pmc1 and the TRP homologue calcium channel Yvc1 (respectively, encoded by the genes PMC1 and YVC1) contributes to control the intracellular calcium availability and the plasma membrane H+-ATPase activation in response to glucose. In strains presenting a single deletion in YVC1 gene or a double deletion in YVC1 and PMC1 genes, both glucose-induced calcium signaling and activation of the H+-ATPase are nearly abolished. These results suggest that Yvc1 calcium channel is an important component of this signal transduction pathway activated in response to glucose addition. We also found that by a still undefined mechanism Yvc1 activation seems to correlate with the changes in the intracellular level of IP3. Taken together, these data demonstrate that glucose addition to yeast cells exposed to low external calcium concentrations affects calcium uptake and the activity of the vacuolar calcium channel Yvc1, contributing to the occurrence of calcium signaling connected to plasma membrane H+-ATPase activation.